Gas Sensor Electrode Coexistence Region Optimization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
NOx sensors face issues with insufficient oxygen decomposition activity and electrode separation from the solid electrolyte body due to poor coexistence region ratios, leading to increased internal resistance and potential gas component decomposition.
Innovation Solution
A sensor element with a pump cell and reference cell, where at least one electrode has a noble metal region, a solid electrolyte body region, and a coexistence region, with an area ratio of the coexistence region between 15.5% and 30%, enhancing oxygen decomposition activity while preventing electrode separation and maintaining stable voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the coexistence region of the electrode is made large to enhance oxygen decomposition activity, then the oxygen decomposition activity is improved, but the electrode separates easily from the solid electrolyte body
Solution Approach 1:
The invention optimizes the area ratio parameter of the coexistence region to a specific range (15.5%-30%) to achieve the best balance between oxygen decomposition activity and electrode joining performance. This parameter optimization resolves the contradiction by finding the precise value that provides sufficient activity while maintaining reliable bonding.
Solution Approach 2:
The electrode is constructed as a composite material containing noble metal particles dispersed in a solid electrolyte body matrix. This composite structure allows the electrode to simultaneously exhibit high oxygen decomposition activity from the noble metal regions and strong joining performance from the solid electrolyte body matrix, resolving the contradiction between activity and reliability.
2Reliability
If the coexistence region of the electrode is made small to prevent electrode separation, then the joining performance is improved, but the internal resistance increases at low temperatures
Solution Approach 1:
The invention sets the coexistence region area ratio within the specific range of 15.5%-30% to prevent internal resistance increase at low temperatures while maintaining joining performance. This parameter control ensures that enough coexistence region remains to maintain low resistance even when the overall coexistence region area is limited for bonding.
Solution Approach 2:
The electrode exhibits different properties in different regions: the noble metal regions provide low resistance and high activity, while the solid electrolyte body regions provide joining performance. The coexistence regions serve as transition zones that locally optimize both properties, resolving the contradiction between joining performance and internal resistance.
3Power
If the coexistence region of the electrode is made excessively large, then the oxygen decomposition activity is enhanced, but oscillation occurs during feedback control
Solution Approach 1:
The invention limits the coexistence region area ratio to less than 30% to prevent oscillation during feedback control while maintaining sufficient oxygen decomposition activity. This parameter constraint ensures that the electrode response remains stable and compatible with feedback control systems, resolving the contradiction between activity and control stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances oxygen decomposition activity, prevents electrode separation, and maintains stable voltage, thereby improving sensor characteristics and preventing gas component decomposition.
Implementation Method 1
an oxygen-ion-conductive solid electrolyte body
Implementation Method 2
the oxygen decomposition activity of the electrode is enhanced
Data Source
AI summary
A sensor element (100) including a measurement chamber (89); a pump cell (83) including a solid electrolyte body (69), an inner electrode (101), and an outer electrode (99); and a reference cell (85). At least one electrode contains a noble metal and a component of the solid electrolyte body. In a cross section, the at least one electrode has a noble metal region (205), a solid electrolyte body region (203), and a coexistence region (207) in which the noble metal and the component of the solid electrolyte body coexist. Further, in the cross section, an area ratio SR of the coexistence region is not less than 15.5% and is less than 30%.